Credit: The Associated Press

FILE - This Jan. 9, 2014 file photo shows a mockup of a Minuteman 3 nuclear missile used for training by missile maintenance crews at F. E. Warren Air Force Base, Wyo. U.S. officials say the number of Air Force service members implicated in a nuclear-force cheating scandal has roughly doubled from the 34 initially cited by the Air Force. It wasn’t immediately clear whether the additional 30-plus airmen implicated in an investigation into cheating on proficiency tests are alleged to have participated in the cheating directly or were involved in some indirect way. (AP Photo/Robert Burns, File)

WASHINGTON — Top defense and military officials worked Wednesday to figure out what systemic personnel problems within the Air Force's nuclear missile corps have caused problems ranging from low morale to cheating and serious security lapses.

Defense Secretary Chuck Hagel gathered senior nuclear leaders from the Air Force and Navy for the first of a series of meetings on the issue, Pentagon press secretary Rear Adm. John Kirby said.